Use the dplyr::do() function and the HELPrct data frame from the mosaicData package to fit a regression model predicting cesd as a function of age separately for each of the levels of the substance variable. Generate a table of results (estimates and confidence intervals) for each level of the grouping variable. SOLUTION library (mdsr) # solution g0es here Use the dplyr::do() function and the HELPrct data frame from the mosaicData package to fit a regression model predicting cesd as a function of age separately for each of the levels of the substance variable. Generate a table of results (estimates and confidence intervals) for each level of the grouping variable. SOLUTION library (mdsr) # solution g0es here